I would put her in a separate tank. Lower the water level so she can reach the surface more easily.

Do DAILY partial water changes. These are necessary to keep the water clean, and help prevent infection. Water changes are the ONLY way to remove toxins, wastes and bacteria which can lead to infections.

If she has 'white fluff' on the wound, she may be developing either Columnaris (a bacterial infection) or Saprolegnia (a fungal/mold infection). Look at the area:
1) Does the white fluff look like it's growing on healthy tissue? This would indicate Colunnaris.
2) Does the fluff look like it's growing on infected, detached, or dying tissue? This would be more indicative of Saprolegnia.

The two conditions are treated with different medications, so if you can figure out which one she has, it can help determine how to treat her.

IMO, the most important things right now are getting her into a separate tank, and providing her with clean water. (Also, lowering the water level so she can reach the surface to breathe.)